Station List

Station 46022 (LLNR 500) - EEL RIVER - 17NM WSW of Eureka, CA Image indicating link to RSS feed of recent meteorological observations for station 46022

Owned and maintained by National Data Buoy Center
3-meter foam buoy w/ seal cage
SCOOP payload
40.716 N 124.540 W (40°42'58" N 124°32'24" W)

Site elevation: sea level
Air temp height: 3.7 m above site elevation
Anemometer height: 4.1 m above site elevation
Barometer elevation: 2.7 m above mean sea level
Sea temp depth: 1.5 m below water line
Water depth: 456 m
Watch circle radius: 667 yards

Latest NWS Marine Forecast

Important Notice to Mariners

Search And Rescue (SAR) Data

Meteorological Observations from Nearby Stations and Ships Image indicating link to RSS feed of recent meteorological observations near station 46022

Large icon indicates selected station.
yellow diamond Stations with recent data
red diamond Stations with no data in last 8 hours
(24 hours for tsunami stations)
Station 46022
Buoy Camera Photos taken at 07/14/2026 0110 UTC. Click photo to enlarge.
Photos from Buoy Camera at station 46022Photos are generally taken hourly during daylight operations.

Conditions at 46022 as of
(7:00 pm PDT on 07/13/2026)
0200 GMT on 07/14/2026:
     

Click on the graph icon in the table below to see a time series plot of the last five days of that observation.

5-day plot - Wind Direction Wind Direction (WDIR): N ( 360 deg true )
5-day plot - Wind Speed Wind Speed (WSPD): 5.8 kts
5-day plot - Wind Gust Wind Gust (GST): 7.8 kts
5-day plot - Atmospheric Pressure Atmospheric Pressure (PRES):30.07 in
5-day plot - Pressure Tendency Pressure Tendency (PTDY):+0.00 in ( Steady )
5-day plot - Air Temperature Air Temperature (ATMP): 55.8 °F
5-day plot - Water Temperature Water Temperature (WTMP): 54.5 °F
5-day plot - Wind Speed at 10 Meters Wind Speed at 10 meters (WSPD10M): 5.8 kts
5-day plot - Wind Speed at 20 Meters Wind Speed at 20 meters (WSPD20M): 7.8 kts
5-day plot - Wind Speed, Wind Gust and Atmospheric Pressure Combined plot of Wind Speed, Gust, and Air Pressure
Supplemental Measurements
Lowest 1-minute Pressure
Time (PDT)Pressure
6:56 pm30.07 in
Highest 1-minute Wind Speed
Time (PDT)5-day plot - 1-Minute Wind Speed WSPD 5-day plot - 1-Minute Wind Direction WDIR
6:52 pm 5.8 kts N ( 360 deg true )
Previous observations
TIME
(PDT)		 5-day plot - Wind Direction
WDIR
 		 5-day plot - Wind Speed
WSPD
kts		 5-day plot - Wind Gust
GST
kts		 5-day plot - Wave Height
WVHT
ft		 5-day plot - Dominant Wave Period
DPD
sec		 5-day plot - Average Wave Period
APD
sec		 5-day plot - Mean Wave Direction
MWD
 		 5-day plot - Atmospheric Pressure
PRES
in		 5-day plot - Pressure Tendency
PTDY
in		 5-day plot - Air Temperature
ATMP
°F		 5-day plot - Water Temperature
WTMP
°F		 5-day plot - Dew Point
DEWP
°F		 5-day plot - Salinity
SAL
psu		 5-day plot - Visibility
VIS
nmi		 5-day plot - Tide (above MLLW)
TIDE
ft
2026-07-13 06:50 pm N 5.8 7.8 4.9 76.0 NW30.07- 55.8 54.5----
2026-07-13 06:40 pm N 5.8 7.8----30.07- 55.8 54.5----
2026-07-13 06:30 pm N 5.8 7.8----30.07- 55.6 54.5----
2026-07-13 06:20 pm N 7.8 7.8 4.6 75.8NNW30.07- 55.6 54.5----
2026-07-13 06:10 pm N 5.8 7.8 4.6-5.8NNW30.06- 55.6 54.5----
2026-07-13 06:00 pm N 7.8 7.8----30.06+0.00 55.6 54.5----
2026-07-13 05:50 pm N 7.8 7.8 4.9 86.0 NW30.06- 55.6 54.5----
2026-07-13 05:40 pm N 7.8 9.7 4.9-6.0 NW30.06- 55.6 54.5----
2026-07-13 05:30 pm N 7.8 9.7----30.06- 55.6 54.5----
2026-07-13 05:20 pm N 9.7 9.7----30.06- 55.6 54.5----
2026-07-13 05:10 pm-------30.07-- 54.5----
2026-07-13 05:00 pm N 11.7 15.5----30.06+0.00 55.8-----
2026-07-13 04:50 pm N 9.7 11.7 4.6 75.7NNW30.07- 55.8 54.3----
2026-07-13 04:40 pm N 9.7 11.7----30.07- 55.6 54.5----
2026-07-13 04:30 pm N 7.8 9.7----30.07- 55.4 54.3----
2026-07-13 04:20 pm N 7.8 9.7 4.9 85.8 NW30.06- 54.9 54.5----
2026-07-13 04:10 pm N 7.8 9.7 4.9-5.8 NW30.07- 54.7 54.3----
2026-07-13 04:00 pm N 7.8 9.7----30.07+0.00 54.7 54.3----
2026-07-13 03:50 pmNNE 5.8 7.8 5.2 85.8 NW30.07- 54.7 54.3----
2026-07-13 03:40 pmNNE 7.8 7.8----30.07- 54.5 54.3----
2026-07-13 03:30 pm N 7.8 9.7----30.06- 54.5 54.1----
2026-07-13 03:20 pm N 9.7 9.7 4.9 85.7 NW30.06- 54.3 54.0----
2026-07-13 03:10 pm N 9.7 11.7 4.9-5.7 NW30.06- 54.3 54.0----
2026-07-13 03:00 pm N 9.7 11.7----30.06+0.00 54.3 53.8----
2026-07-13 02:50 pm N 9.7 11.7 5.2 85.8 NW30.05- 54.3 53.6----
2026-07-13 02:40 pm N 11.7 13.6----30.06- 54.1 53.6----
2026-07-13 02:30 pm N 11.7 13.6----30.06- 54.1 53.6----
2026-07-13 02:20 pm N 11.7 13.6 4.9 85.6 NW30.06- 54.1-----
2026-07-13 02:10 pm N 13.6 15.5----30.06- 54.0 53.2----
2026-07-13 02:00 pm N 13.6 15.5----30.06+0.02 54.1 53.1----
2026-07-13 01:50 pm N 13.6 15.5 5.2 75.6NNW30.06- 54.0 53.1----
2026-07-13 01:40 pm N 13.6 15.5----30.06-- 53.1----
2026-07-13 01:30 pm N 11.7 15.5----30.06- 53.6 52.7----
2026-07-13 01:20 pm N 11.7 15.5----30.06- 53.6-----
2026-07-13 01:10 pm N 13.6 17.5----30.06- 53.4 52.7----
2026-07-13 01:00 pm N 13.6 15.5----30.06+0.02 53.2 52.7----
2026-07-13 12:50 pm N 11.7 15.5 5.9 75.6NNW30.06- 53.2 52.7----
2026-07-13 12:40 pmNNW 13.6 15.5 5.9-5.6NNW30.07- 53.1 52.7----
2026-07-13 12:30 pm N 13.6 17.5----30.06- 52.7 52.5----
2026-07-13 12:20 pm N 11.7 15.5 5.2-5.4 NW30.07- 52.7 52.5----
2026-07-13 12:10 pm--- 5.2 85.4 NW--------
2026-07-13 12:00 pm N 11.7 15.5----30.06+0.01 52.5-----
2026-07-13 11:50 am N 13.6 15.5 5.6-5.6 NW30.06- 52.3 52.5----
2026-07-13 11:40 am--- 5.6 95.6 NW--------
2026-07-13 11:30 am N 11.7 13.6----30.06- 52.3 52.5----
2026-07-13 11:20 am N 11.7 15.5 5.2 65.3NNW30.06- 52.3 52.5----
2026-07-13 11:10 am N 13.6 15.5----30.05- 52.3 52.5----
2026-07-13 11:00 am N 15.5 17.5----30.05+0.02 52.3 52.5----
2026-07-13 10:50 am N 13.6 15.5 5.9 95.4 NW30.04- 52.2 52.7----
2026-07-13 10:40 am N 15.5 17.5----30.04- 52.5 52.7----
2026-07-13 10:30 am N 15.5 17.5----30.04- 52.7 52.7----
2026-07-13 10:20 am N 13.6 17.5 5.6 95.3NNW30.05- 52.9 52.7----
2026-07-13 10:10 am N 15.5 19.4 5.6-5.3NNW30.05- 52.9 52.7----
2026-07-13 10:00 am N 15.5 17.5----30.04+0.02 52.9 52.7----
2026-07-13 09:50 am N 13.6 17.5 5.9 65.4NNW30.04- 52.9 52.7----
2026-07-13 09:40 am N 13.6 17.5----30.05- 52.9 52.7----
2026-07-13 09:30 am N 13.6 17.5----30.04- 52.9 52.7----
2026-07-13 09:20 am N 15.5 19.4 5.6 95.4 NW30.05- 52.9 52.9----
2026-07-13 09:10 am N 17.5 19.4 5.6-5.4 NW30.04- 53.1 52.9----
2026-07-13 09:00 am N 15.5 19.4----30.04+0.01 53.1 53.1----
2026-07-13 08:50 am N 15.5 19.4 5.2 85.3 NW30.04- 52.9 53.1----
2026-07-13 08:40 am N 15.5 19.4 5.2-5.3 NW30.04- 53.1 53.1----
2026-07-13 08:30 am N 15.5 19.4----30.03- 53.1 53.1----
2026-07-13 08:20 am N 15.5 19.4 5.9 85.7 NW30.03- 53.1 53.2----
2026-07-13 08:10 am N 15.5 17.5 5.9-5.7 NW30.03- 53.2 53.2----
2026-07-13 08:00 am N 13.6 17.5----30.02+0.00 53.4 53.2----
2026-07-13 07:50 am N 13.6 15.5 5.6 75.6NNW30.03- 53.4 53.2----
2026-07-13 07:40 am N 13.6 15.5----30.03- 53.4 53.2----
2026-07-13 07:30 am N 13.6 15.5----30.03- 53.4 53.2----
2026-07-13 07:20 am N 15.5 19.4 5.6 95.5 NW30.03- 53.6 53.2----
2026-07-13 07:10 am N 15.5 19.4 5.6-5.5 NW30.02- 53.8 53.2----
2026-07-13 07:00 am N 15.5 17.5----30.02+0.00 54.0 53.4----
2026-07-13 06:50 am N 15.5 19.4 5.6 85.7NNW30.02- 54.0 53.4----
2026-07-13 06:40 am N 15.5 19.4----30.03- 54.1 53.4----
2026-07-13 06:30 am N 13.6 17.5----30.03- 54.3 53.4----
2026-07-13 06:20 am N 15.5 19.4 5.2 75.7NNW30.03- 54.5 53.4----
2026-07-13 06:10 am N 13.6 17.5----30.03- 54.5 53.4----
2026-07-13 05:50 am N 15.5 17.5 5.6 95.9 NW30.03- 54.5 53.2----
2026-07-13 05:40 am N 13.6 17.5----30.03- 54.5 53.2----
2026-07-13 05:30 am N 13.6 17.5----30.03- 54.5 53.2----
2026-07-13 05:20 am N 13.6 17.5 5.2 85.9 NW30.03- 54.5 53.2----
2026-07-13 05:10 am N 13.6 17.5 5.2-5.9 NW30.03- 54.5 53.2----
2026-07-13 05:00 am N 15.5 17.5----30.03+0.00 54.7 53.4----
2026-07-13 04:50 am N 13.6 17.5 5.2 76.0 NW30.03- 54.7 53.4----
2026-07-13 04:40 am N 13.6 17.5 5.2-6.0 NW30.03- 54.7 53.6----
2026-07-13 04:30 am N 13.6 19.4----30.02- 54.7 53.6----
2026-07-13 04:20 am N 13.6 17.5 5.2 96.2WNW30.02- 54.7 53.6----
2026-07-13 04:10 am N 13.6 17.5 5.2-6.2WNW30.02- 54.7 53.6----
2026-07-13 04:00 am N 11.7 15.5----30.02+0.00 54.5 53.8----
2026-07-13 03:50 am N 9.7 11.7 4.9 96.0 NW30.02- 54.3 54.0----
2026-07-13 03:40 am N 9.7 9.7----30.02- 54.3 54.0----
2026-07-13 03:30 am N 7.8 9.7----30.03- 54.3 54.0----
2026-07-13 03:20 am N 9.7 9.7 5.2 96.0 NW30.03- 54.5 54.0----
2026-07-13 03:10 am N 9.7 11.7----30.02- 54.5 54.1----
2026-07-13 03:00 am N 9.7 11.7----30.02-0.01 54.7-----
2026-07-13 02:50 am N 9.7 11.7 4.9 75.7NNW30.02- 54.7 54.1----
2026-07-13 02:40 am N 11.7 13.6----30.02- 54.7 54.1----
2026-07-13 02:30 am N 11.7 13.6----30.02- 54.7 54.1----
2026-07-13 02:20 am N 11.7 13.6 5.2 75.9NNW30.02- 54.9 54.1----
2026-07-13 02:10 am N 9.7 11.7 5.2-5.9NNW30.01- 54.9 54.1----
2026-07-13 02:00 am N 9.7 11.7----30.02-0.03 54.9 54.1----
2026-07-13 01:50 am N 9.7 11.7 5.6 75.9NNW30.03- 54.9 54.1----
2026-07-13 01:40 am N 9.7 11.7----30.02- 54.9 54.3----
2026-07-13 01:30 am N 9.7 11.7----30.03- 54.9 54.3----
2026-07-13 01:20 am N 9.7 11.7 5.6 75.9NNW30.03- 54.9 54.3----
2026-07-13 01:10 am N 9.7 11.7 5.6-5.9NNW30.03- 54.9 54.3----
2026-07-13 01:00 am N 9.7 13.6----30.03-0.02 54.9 54.3----
2026-07-13 12:50 am N 9.7 11.7 4.9 75.8NNW30.03- 54.9 54.3----
2026-07-13 12:40 am N 9.7 11.7 4.9-5.8NNW30.03- 54.7 54.1----
2026-07-13 12:30 am N 9.7 11.7----30.03- 54.7 54.1----
2026-07-13 12:20 am N 9.7 11.7 5.6 85.9 NW30.03- 54.7 54.3----
2026-07-13 12:10 am N 7.8 9.7 5.6-5.9 NW30.03- 54.7 54.3----
2026-07-13 12:00 am N 7.8 9.7----30.03-0.01 54.7 54.3----
2026-07-12 11:50 pm N 7.8 9.7 4.9 86.0 NW30.03- 54.7 54.3----
2026-07-12 11:40 pm N 7.8 9.7----30.04- 54.7 54.5----
2026-07-12 11:30 pm N 7.8 9.7----30.04- 54.9 54.5----
2026-07-12 11:20 pmNNE 7.8 9.7 5.2 85.8 NW30.04- 54.9 54.5----
2026-07-12 11:10 pmNNE 7.8 9.7----30.04- 54.9 54.5----
2026-07-12 11:00 pm N 9.7 11.7----30.05+0.00 55.0 54.5----
2026-07-12 10:50 pm N 9.7 11.7 5.2 85.9 NW30.05- 55.0 54.7----
2026-07-12 10:40 pm N 9.7 11.7----30.05- 55.0 54.7----
2026-07-12 10:30 pm N 9.7 11.7----30.05- 55.0 54.7----
2026-07-12 10:20 pm N 9.7 11.7 5.6 95.8 NW30.05- 55.0 54.9----
2026-07-12 10:10 pm N 9.7 11.7 5.6-5.8 NW30.06- 55.0 54.7----
2026-07-12 10:00 pm N 9.7 11.7----30.05+0.00 55.2 54.5----
2026-07-12 09:50 pm N 11.7 13.6 5.9 86.0 NW30.05- 55.4 54.3----
2026-07-12 09:40 pm N 13.6 15.5----30.04- 55.4 54.1----
2026-07-12 09:30 pm N 13.6 15.5----30.04- 55.6 54.1----
2026-07-12 09:20 pm N 13.6 15.5 5.2 95.8 NW30.04- 55.6 54.1----
2026-07-12 09:10 pm N 13.6 15.5 5.2-5.8 NW30.05- 55.6 53.8----
2026-07-12 09:00 pm N 13.6 15.5----30.04+0.00 55.8 54.0----
2026-07-12 08:50 pm N 11.7 15.5 5.2 95.9 NW30.05- 55.8 53.8----
2026-07-12 08:40 pm N 11.7 13.6----30.05- 55.8 53.8----
2026-07-12 08:30 pm N 11.7 13.6----30.05- 55.9 54.1----
2026-07-12 08:20 pm N 11.7 13.6 5.6 96.0 NW30.05- 55.9 54.1----
2026-07-12 08:10 pm N 11.7 15.5----30.05- 56.1 54.1----
2026-07-12 08:00 pm N 13.6 15.5----30.05+0.00 56.1 54.1----
2026-07-12 07:50 pm N 11.7 15.5 5.6 96.2 NW30.05- 56.1 54.1----
2026-07-12 07:40 pm N 9.7 13.6----30.05- 55.9 54.0----
2026-07-12 07:30 pm N 9.7 11.7----30.05- 55.9 54.1----
2026-07-12 07:20 pm N 9.7 11.7 5.6 96.0 NW30.05- 55.9 54.1----
2026-07-12 07:10 pm N 9.7 11.7 5.6-6.0 NW30.05- 55.9 54.1----
2026-07-12 07:00 pm N 9.7 11.7----30.05-0.01 55.9 54.1----
2026-07-12 06:50 pm N 9.7 11.7 5.9 76.2NNW30.05- 55.9 54.0----
Wave Summary
for 46022 as of
(6:40 pm PDT on 07/13/2026)
0140 GMT on 07/14/2026:

These wave data are displayed in rounded times.

     

Click on the graph icon in the table below to see a time series plot of the last five days of that observation.

5-day plot - Significant Wave Height Significant Wave Height (WVHT): 4.9 ft
5-day plot - Swell Height Swell Height (SwH): 4.6 ft
5-day plot - Swell Period Swell Period (SwP): 7.1 sec
5-day plot - Swell Direction Swell Direction (SwD): NW
5-day plot - Wind Wave Height Wind Wave Height (WWH): 1.3 ft
5-day plot - Wind Wave Period Wind Wave Period (WWP): 3.1 sec
5-day plot - Wind Wave Direction Wind Wave Direction (WWD): N
5-day plot - Wave Steepness Wave Steepness (STEEPNESS): STEEP
5-day plot - Average Wave Period Average Wave Period (APD): 6.0 sec
Previous observations
TIME
(PDT)		 5-day plot - Wave Height
WVHT
ft		 5-day plot - Swell Height
SwH
ft		 5-day plot - Swell Period
SwP
sec		 5-day plot - Swell Direction
SwD
 		 5-day plot - Wind Wave Height
WWH
ft		 5-day plot - Wind Wave Period
WWP
sec		 5-day plot - Wind Wave Direction
WWD
 		 5-day plot - Wave Steepness
STEEPNESS
 		 5-day plot - Average Wave Period
APD
sec
2026-07-13 06:10 pm 4.6 4.3 6.7NNW 1.3 3.6 NNW STEEP 5.8
2026-07-13 05:40 pm 4.9 4.6 8.3 NW 1.3 3.6 NNW AVERAGE 6.0
2026-07-13 04:40 pm 4.6 4.3 6.7NNW 1.6 3.7 NNW STEEP 5.7
2026-07-13 04:10 pm 4.9 4.6 8.3 NW 1.6 3.8 NW AVERAGE 5.8
2026-07-13 03:40 pm 5.2 4.9 8.3 NW 1.6 3.7 NNW AVERAGE 5.8
2026-07-13 03:10 pm 4.9 4.6 8.3 NW 2.0 3.7 NNW AVERAGE 5.7
2026-07-13 02:40 pm 5.2 4.6 8.3 NW 2.6 5.3 NNW AVERAGE 5.8
2026-07-13 02:10 pm 4.9 3.6 8.3 NW 3.3 6.2 NNW AVERAGE 5.6
2026-07-13 01:40 pm 5.2 3.9 7.1NNW 3.3 5.9 NNW STEEP 5.6
2026-07-13 12:40 pm 5.9 3.9 7.1NNW 4.3 5.6 NNW STEEP 5.6
2026-07-13 12:10 pm 5.2 3.6 8.3 NW 3.9 6.2 NNW AVERAGE 5.4
2026-07-13 11:40 am 5.6 4.3 9.1 NW 3.6 4.8 NNW AVERAGE 5.6
2026-07-13 11:10 am 5.2 3.0 8.3 NW 4.3 6.2 NNW STEEP 5.3
2026-07-13 10:40 am 5.9 3.0 9.1 NW 4.9 5.9 NNW AVERAGE 5.4
2026-07-13 10:10 am 5.6 2.6 9.1NNW 4.9 5.6 NNW AVERAGE 5.3
2026-07-13 09:40 am 5.9 3.3 9.1NNW 4.9 5.9 NNWVERY_STEEP 5.4
2026-07-13 09:10 am 5.6 2.6 9.1 NW 4.9 7.1 NNW AVERAGE 5.4
2026-07-13 08:40 am 5.2 3.0 8.3 NW 4.6 7.1 NNW AVERAGE 5.3
2026-07-13 08:10 am 5.9 3.6 8.3 NW 4.6 6.2 NNW AVERAGE 5.7
2026-07-13 07:40 am 5.6 4.3 6.7NNW 3.3 5.6 NNW STEEP 5.6
2026-07-13 07:10 am 5.6 3.3 9.1 NW 4.6 7.1 NNW AVERAGE 5.5
2026-07-13 06:40 am 5.6 3.3 13.8 SW 4.6 7.7 NNW AVERAGE 5.7
2026-07-13 06:10 am 5.2 3.9 7.1NNW 3.9 5.9 NNW STEEP 5.7
2026-07-13 05:40 am 5.6 3.9 9.1 NW 3.9 6.7 NNW AVERAGE 5.9
2026-07-13 05:10 am 5.2 3.9 8.3 NW 3.6 5.9 NW AVERAGE 5.9
2026-07-13 04:40 am 5.2 4.3 7.1 NW 3.0 5.6 NNW STEEP 6.0
2026-07-13 04:10 am 5.2 3.9 9.1WNW 3.6 5.9 NNW AVERAGE 6.2
2026-07-13 03:40 am 4.9 4.9 9.1 NW 1.6 4.3 NW AVERAGE 6.0
2026-07-13 03:10 am 5.2 4.9 9.1 NW 1.6 4.0 NW AVERAGE 6.0
2026-07-13 02:40 am 4.9 4.3 6.7NNW 2.6 5.3 NNW STEEP 5.7
2026-07-13 02:10 am 5.2 4.9 6.7NNW 2.3 4.2 NNW STEEP 5.9
2026-07-13 01:40 am 5.6 4.9 6.7NNW 2.0 4.5 NW STEEP 5.9
2026-07-13 01:10 am 5.6 5.2 6.7NNW 2.0 4.2 NNW STEEP 5.9
2026-07-13 12:40 am 4.9 4.6 7.1NNW 2.0 4.3 NNW STEEP 5.8
2026-07-13 12:10 am 5.6 5.2 8.3 NW 1.6 3.4 NNW AVERAGE 5.9
2026-07-12 11:40 pm 4.9 4.9 8.3 NW 1.6 3.8 NNW AVERAGE 6.0
2026-07-12 11:10 pm 5.2 4.9 8.3 NW 1.6 3.4 NNW AVERAGE 5.8
2026-07-12 10:40 pm 5.2 4.9 7.7 NW 2.3 4.5 NNW AVERAGE 5.9
2026-07-12 10:10 pm 5.6 4.9 9.1 NW 2.3 4.3 NNW AVERAGE 5.8
2026-07-12 09:40 pm 5.9 4.6 8.3 NW 3.6 5.9 NNW AVERAGE 6.0
2026-07-12 09:10 pm 5.2 4.3 9.1 NW 3.0 5.0 NW AVERAGE 5.8
2026-07-12 08:40 pm 5.2 4.6 9.1 NW 2.6 5.6 NNW AVERAGE 5.9
2026-07-12 08:10 pm 5.6 4.6 9.1 NW 3.3 5.0 NNW AVERAGE 6.0
2026-07-12 07:40 pm 5.6 5.2 9.1 NW 2.3 4.8 NW AVERAGE 6.2
2026-07-12 07:10 pm 5.6 4.9 9.1 NW 2.6 4.8 NW AVERAGE 6.0

Plot icon Plot of wave energy versus frequency (and period)